Carbon black process



J. C. KREJCI CARBON BLACK PROCESS Filed Dec.

Nov. 4, 1952 FIG. 2

INVENTOR JOSEPH C. KREJCI M ATTORNEY Patented Nov. 4, 1952 2,616,794 CARBON BLAQK PROCESS Joseph-C. Krejci, Phillips, Tex., assignor to PhillipsPetroleum Company, a corporation of Delaware Application December 225 1950, serisrnouzcarzc 13 Claims. ("01. 23-209;6)

This invention relates to a process for produc ing, carbon black,.and more particularly it relates Still another object of this invention is to provide a carbon black making process which is to a method for producing. carbon black by the x b in e a o sp ciallyin the re pect incomplete combustion. of carbonaceous gases that a, =p O Q of essentially a S P P and vapors or by decomposition thereof bycontact; with hot. gases;

Attention is directed to U. S. Patents No.

2,375,796, issued May. 1945.; No. 2,375,798,

issued May 15, 19.45; and No. 2,419,565, issued April .29, 1947, wherein related subject matter is disclosed. This application is acontinuationin-part of my copending application, Serial No.

7 materials merely by alteration and control of 571,655, filed Januaryfi, 1945 (now abandoned),

which application isa divisionpf my application,

SerialNo. 424,084, filed December 22, 1941 andl issued May 15,1945, as U. S. Patent 2,375,795.

At, the present time, most of the carbon blacks of commerce areproduced by a very few processes and these blacks may be grouped into classes depending upon the typesof rubber compound and vulcanized rubber which the carbon blacks willproduce. A soft carbon black as compared to a hard carbon black is one which when mixed in a conventional rubber compound and then vulcanized yields a product which is softer, more resilient, more rubbery and yet tough whereas a hard carbon black in the same compound imparts .stiifer, tougher characteristics, with lower resilience.

These two types of carbon black may be considered essentially as limits and many of the carbon blacks produced will possess hardness properties intermediate these above limits.

The commercial fchannelf process produces a hard type carbon black which is especially good forcompounding automotive tire tread stocks that withstand abrasion and possess good physical test properties. However, the yield of carbon by this process is only about 3.5% of the carbon content of the gas from which it is made. so e other carbon black processes give higher yields of carbon than the channel process, but in essentially all casesthese blacks are of a softer type and less desirable for use in good quality tire tread stocks. find other and varied uses, which are minor as compared to the relatively large amounts of hard channel black which go into tires at the present time and a process which would 'give a high yield of a hard black "'simila'rto channel black in properties, would be most desirable.

The principal object of this invention is to provide an apparatusand a process for producing carbon black of high yield and of quality comparable to or superior'to the present day channel black for use in tire stock's.--

Another object of this invention is to improve on thepresent day art of producing carbon black by providing an apparatus and a process which will produce carbon black out of contact with sol-id surfaces without depending on maintenance of streamline flow conditions as in some other processes, and with an extremely short reaction These latter blacks, however,-

the operating conditions.

Still other objects and advantages will beapparent to those skilled in the artfrom acareful study of the following description and disclosure.

The accompanying diagrammatic drawings are a part of this specification and illustrate preferred forms of the apparatus for carrying. out

. my invention, which:

Figure 1 is a longitudinal section of a preferred form of the reaction chamber along the line the same or similar parts. These drawings have been presented in diagrammatic form only, and

such conventional and Well known parts as valves, flowmeters, pressure regulators; temperature measuring devices, etc., for simplicity have not been shown.

Referring to the figures,the cylindrical reactionchamber II] has a lining H of highly refracto'ry material Such assillimanite o'r Alunduin. Between this refractory liner H and the cylindrical steel shee'li'l3 is a layer of insulation l2. 'The ratio of thel'ength to the diameter of the good results.

chamber has not been found to be critical, ratios ranging from 2 to 10 have been found to give The chamber is equipped with a fuel burner [5 extending through the chamber wall and terminating in an ovalshaped opening such that the incoming gaseous mixture" enters the reaction chamber tangential to the inside cylindrical surface-bf the chamber and perpendicul'a'r to the longitudinal axis thereof. The temperature within the chamber may be measured through one or inoreopenings, as 20. At the inlet end, the chamber is equipped with inlet tube I6 which is in line with the longitudinal axis. If one gas only is admitted to the inlet end of the chamber, this tube; i 6 extends through the refractory, insulation and shell, but in case a mixture of two gases is admitted, a Y I9 is used, one of the gases being introduced through arm I! and the other through arm [8 withtube [6 in this case serving as a mixing tube "as well as the chamber inlet tube. Tubes 2| from the preheat furnace carrying the reactant gas and air are connected to the Y as shown in Figures 1 and 3.

Figures 3 and 4 illustrate the reaction chamber in the main as in Figure 1, but with some modifications which I have found advantageous. The use of two or three additional tangential burners [5, as in Figure 3, permits a more nearly uniform distribution of heat throughout the length of the chamber, and in addition reduces by as much as 30% the total fuel required to keep the chamber walls free of carbon. When two or more tangential burners I5 are used it is not necessary that they be equal in size, since it has been found advantageous to introduce most of the fuel through a larger burner IE5 at the inlet end of the chamber and to use several small burners throughout the length of the chamber as an aid in preventing carbon deposition. In this Way the reactant gas comes into contact with a greater portion of the fuel throughout the length of the chamber.

In the apparatus embodiment shown in Figure 3, a modifiication of the chambers cross section by insertion of conical shape 22 has been found valuable as a means of regulating the extent of mixing between the reactant gas and the tangential burner flame to any desired degree.

The introduction of air tangentially'into the annular space 23 around mixing inlet tube [5 by means of tube 24, as in the chamber modification shown in Figure 3, has been found suitable as a means for the prevention of carbon deposition on the back Wall 25. Due to the centrifugal force imparted by the tangential motion, the air spreads out on emerging from the annular space 23 and blankets the back wall of the chamber thus keeping the reactant gas out of contact with the wall. The mixing tube [6 and the annular duct or space 23 were extended into the chamber for convenience in installation of air tube 24. The annular space 26 surrounding the back wall may be filled with a refractory material, if desired.

The reaction or chamber products exit from the open end of the reaction chamber, and are immediately cooled. Applicant has found that a spray of water absorbs sufiicient heat to cool said products suiiiciently below the temperature at which the carbon black particles continue to grow. A water spray I4 is shown diagrammatically inFigures 1 and 3.

In the carrying out, or operating, according to my invention, a mixture of fuel such as natural gas and air is introduced through tangential burner or burners 5 at sufficient velocity to cause the flame to adhere to the inside surface of the chamber and form a blanket of flame and products of combustion over the chamber wall throughout its length. Velocities of the incoming gaseous mixture through the tangential burner ports may vary over wide limits, but must necessarily be rather high in case the gaseous fuel and air are mixed in explosive proportions.

In this case, the rate of flow of this fuel must be faster than the linear rate of flame propagation in said fuel mixture to prevent an explosion. Applicant has found that this velocity of tangential gas flow may vary from as low as 30 feet per second or less to 200 feet per second, or even more. In one test, best results were obtained by maintaining this fuel gas velocity within the range of 100 to 150 feet per second, When air Y gential flame.

alone is used as the tangential gas, carbon is easily prevented from depositing on the chamber walls even at very low tangential velocities. Thus it is seen that the tangential gas may vary between wide limits of composition, ranging from air alone on the one hand to the theoretical mixture of combustible gas and air on the other hand, or even richer than the theoretical mixture provided the mixture is not so rich as to permit carbon deposition on the chamber side walls.

The tangential fuel velocity should be rather high to maintain by centrifugal force a layer or blanket of name and combustion products on the inside of the chamber wall. The tangential fiame and combustion products travel from the tangential burner inlet toward the outlet end of the reaction chamber Hl following a helical path adjacent the inside wall of said reaction chamber thereby forming essentially a continuous layer or blanket or name and combustion products on said inside wall. This layer or blanket of flame serves as a separating medium to prevent contact of the central contents of the chamber and the side walls.

A carbon bearing gas such as natural gas or a mixture of such gas and air with less than sufficient air for complete combustion is introduced into the reaction chamber l0 through tube [6. The carbon bearing gas and the oxygen bearing gas passed through the said inlet tube 16 W111 be hereinafter referred to as a reactant gas and reactant air, respectively. If reactant air is not mixed with the incoming reactant gas at this oint for furnishing endothermic heat to the re actants after they enter the reaction chamber, said heat of reaction is then supplied by the tan- The tube l6 directs the reactants along the longitudinal axis of the chamber and this in addition to the effect of the tangential flame which keeps the reactant gas away from the walls of the chamber assures that the reaction to carbon takes place in the central core of ,tube furnace or other type of furnace or other.

the chamber. In operations when oxygen containing gas is mixed with the reactant gas and tube I6 serves as the mixer, it should be sufficiently large to mix them eifectively and still not '2 so large that the period of detention of the gaseous mixture in the tube is long enough to permit decomposition so extensive as to result in an inordinately rapid deposition of any portion of the reactant gas to carbon which would in turn accumulate in the tube.

Experiments in which the oxygen bearing gas was air, revealed that periods of detention of less than 0.005 second in the mixer were satisfactory, premature carbon deposition being virtually eliminated in many cases when both reactant gas and reactant air were preheated to a temperature of the order of 2000 F., the gas being a natural gas containing 35 pounds of carbon per 1000 cubic feet. The preheating furnace may be a heating means of suitable design and such that the gases undergoing preheating may be heated to temperatures within the range of say 1000 to 2800 F. or even more, and such that the heated gases issuing therefrom may be at a constant,

pheric temperature, that is, without preheating.

aeiewioa 'Carbonblack' yields were higher under these conditions than usually obtained in present day practice, but applicant prefers to preheat the reactant gases in order to obtain maximum yields of black.

In one experiment in which the same natural gas was used in the fuel to the tangential burner and as reactant gas, the minimum tangential fuel required to maintain the chamber wall free of carbon had to per cent as much natural gas as was used as reactant gas. The amount of tangential burner fuel required to prevent carbon deposition increased as the ratio of reactant air to reactant gas was decreased. In this above referred to experiment, the retention time in the chamber was approximately 0.1 second. While this particular retention time was held to about 0.1 second, it was found that the said retention time may be varied depending upon other conditions from 0.005 second to as long as 0.4 second, or even 1 second, and still obtain good qualityhigh yield carbon black. The temperature within the chamber may be varied Within wide limits, as for example, the chamber temperature in the above referred to experiment was arbitrarily held within the range of 2000 to 3300 F., better yields of excellent quality hard black resulted from operating periods when temperatures were of the order of 2300 to 2600 F., however, high yields were obtained at chamber temperatures as high as 3100 F., and at temperatures lower than 2200" F. At all of the above-mentioned temperatures gases covering the walls serve as a mechanical separator or partition to prevent contact of the reactant gases with the chamber sidewalls.

'By' using my process, yields as high as per cent of the carbon content of the reactant gas have been obtained, which is, however exceptionally high. Yields can be made to vary between relatively Wide limits with a minimum of effecton the quality of carbon black produced. The black produced by my process possesses qualities equal to and in many ways superior to the channel black of commerce which black is the accepted measure of quality for rubber tire tread stocks. The main use for black is in the rubber industry, and only certain blacks, that is, carbon black .made by certain processes, possess the proper properties to yield commercially good rubber. In the main, carbon black made by the channel process, or as it is commonly called, channel black, is the black largely used by rubber tire manufacturers in very large quantities. To determine the quality of carbon black as regards the manufacture of rubber or tires, it is necessary to prepare a batch of compound incorporating therein the carbon black in question, vulcanize the mixture and make the conventional tests on the vulcanized product.

Table I shows operating data taken when manufacturing carbon black from natural gas containing 35 pounds of carbon per 1000 cubic feet when using my apparatus and according to my process.

Table I Yield Tangential Reactants, Cu. gt f Ft. Per Hr. 1 3 33 1. Reaction ur e Ohamber- Reactant Gas Total Gas Run No. glee- Temp GDIIL, o F O F- a Gas Air Gas 1libspg r P31200111; Ilxllbscpg r Pgigccelnt 61 2 4. B R 2 000 200 0 60 660 11 2 3 8 6 2 6 B57 2, 000 200 0 80 880 2, 470 10. 0 28. 6 7. 0 20. 0 B64 2, 000 200 0 100 l, 100 4. 6 l3, 1 3.1 8. 9 B46R 1 2, 000 200 200 60 660 6.0 17. 1 4. 7 13. 4 B54 2, 000 200 200 80 880 2, 530 6.1 17.4 4. 4 12.6 B56 2, 000 200 300 60 660 2, 550 4. 2 12.0 3. 3 9. 4 B L 2, 000 200 400 50 550 3. 0 8. 6 2. 4 6. 9 B99 2,000 200 0 80 2 880 2, 700 7. 8 22. 3 5. 6 16.0 B206 2, 0 l, 200 0 600 6, 600 9. 2 26. 3 6. 1 17. 4 B208 2, 000 1, 200 0 700 7, 700 9. 8 28.0 6. 2 l7. 7 B209 2, 000 1, 600 0 700 7, 700 10. 7 30. 5 7. 5 21. 4

1 This test was made in a furnace or chamber four and one-half inches inside diameter by twenty-two inches in length.

2 Preheated to 2000 F.

a This test was made in a furnace or chamber nine and one-half inches inside diameter by forty-six inches in length.

andtemperature ranges carbon black yields were higher than from the conventional channel process. These operating temperatures, retention time, etc., are not intended to be definite and limiting conditions, since experiments haveindicated that operating conditions may be varied within wide limits and yet obtain extraordinarily high yields of carbon black of quality equal to or superior to the high quality channel black of commerce.

The herein disclosed tangential flame serves several purposes and its proper use makes possible continuous operation of my apparatus without depositionof carbon on the chamber walls. The reaction chamber must be maintained at a relatively high temperature to cause the carbon forming reaction to take place. By the introduction of a gas and air mixture through the tangential burners a sheet of flame covers the walls and the deposition of carbon thereupon is prevented by combustion and/or water gas reac- In the above runs, 361R. and 346R, the amount 55 of fuel used in the tangential burner was not sufficient to keep the chamber wall free of carbon. Reactant gas and reactant air were heated individually in the preheat furnace and to the same temperature, as recorded in the second column of Table I. In all tests or runs excepting run B99,

the gas and air to the tangential burner were not preheated, that is, the fuel mixture entered the said burner at atmospheric temperature. In run B99, however, the air portion of the tangential fuel was preheated to 2000 F. It might be mentioned, also, that while it is not necessary, the tangential burner fuel was composed of air and gas in the theoretical ratio for complete combustion to carbon dioxide and water.

It should be noted from the above data that the carbon black yields are exceptionally high, and especially so when considering the 3.5% yield of the commercial channel process when treating a natural gas of 35 pound carbon content. It

tions, Still more important, the-tangentially fed"'75"mi'ght' bemoted also that the higher yields of 7. black were obtained when the reactant gases contained no air or as termed above, no reactant air. From the above data, it seem-s that the less reactant air used with a given amount of reactant gas, the higher the carbon black yield. In addition, a relation also seems to exist between the amount of combined tangential air and gas and the carbon black yield.

Carbon black has been made by commercial processes with yields as high as 50% of the carbon content of the gas, but in such cases, the carbon black did not have the reinforcing properties of channel black. In fact, such black is very inferior for rubber tire making purposes to the carbon black made as herein disclosed and to compare its properties with those of channel black, batches of rubber compound were prepared according to the compounding formula, as follows:

Parts by weight Parts by weigh Smoke sheet N 100 Stearic acid 3 5O Phenylfinaphthylamine 1 5 Captax 0.9 3 Pine tar- 3 Table II Mogulus, lfOLgldS B k gcetone er sq. nc rea xtract- 5 52? pounds Elonga- Resiable on Sample at 9740}, Per tion, Per lie-nee. Original i Square cent per cent Carbon 200% 500% In Black.

per cent;

E64 60 1,000 3, 770 4,100 530 80. 7 .(ll

Channel Black: Hard Black"... 60 760 3,190 4, 270 603 75. 0

Furnace Black: Soft Black 60 370 2, 970 3, 230 530 87.0

the low yield channel black and therefore found Table III, below, shows additional rubber tests only a limited market for other purposes.

One of the outstanding advantages of my process lies in the fact that although the yield is high, a black can be produced of a quality satisfactory for tire tread purposes and in some properties superior to conventional channel black.

The channel black of commerce is used herein as a standard of tire tread stock quality since black made by that process is acceptable to the tire manufacturers. To illustrate the quality of using carbon black made according to my process and in my apparatus. These results diiIer from those of Table II in that the vulcanizations were made at 260 F., for the times indicated. The resilience test samples were also vulcanized at 260 F., and for a period of '70 minutes. The resilience values as given for samples containing my carbon black and vulcanized at 260 F'., are essentially the same as for those vulcanized at 274 F.

Table III Modulus, Pounds Acetone vu1cani Per sq. Inch Break, Extract- Zatlon pounds Elonga- Resiable on Sample at 0 a Per tion, Per lience, Original Minutes" square cent per cent Carbon 200% 500% In Black,

per cent 90 990 3, 810 3, 985 515 l 30 560 2, 750 4, 300 657 B208 l 60 760 3, 490 4, 150 568 83. 4

90 870 3, 930 4, 510 557 20 340 l, 850 3, 120 670 30 440 2, 370 3, 510 635 Furnace Black: Soft Black 600 2, 640 3, 600 610 87.1 .25

In Tables II and III, by the word vulcanization, heading the second column, is meant the length of time that the compound containing smoked sheet, carbon black, etc., is heated at the vulcanization temperature; in Table II, the vulcanizing temperature is 274 F. and in Table III it is 260 F., and the time is recorded in minutes. The 200% modulus column refers to the pounds per square inch pull in a tension test when the test piece of vulcanized rubber has been stretched 200% of the length of the originaltest piece; the 500% modulus refers to the pounds per square inch pull in a similar tension test when the test piece has been stretched 500% of its original length. The Break column represents the pounds per square inch pull at, the point of rupture or break of the test piece undergoing the above-mentioned 200% and 500% modulus tests. The Elongation column represents the stretch or elongation at the point of break. The Resilience is the complement of the hysteresis loss, or more simply expressed is a measure of the potential energy of a piece of rubber that is present as a result of applied stress and which is recoverable when the stressis removed.

'The Acetone Extractable is the per cent loss in weight of the original carbon black upon extraction with acetone.

In addition to the tests on rubbers made with my carbonblack, samples containing hard and soft blacks made by the Channel and Furnace processes, respectively, are included in Table II and a Furnace Black (soft black) in Table III for comparison.

Upon consideration of the data of Table II, the modulus, break, elongation and resilience values of the channel black sample are characteristic of a hard black. Similarly, the data pertaining to the furnace black-sample are characteristic of a "soft blac Based upon this classification, it. is obvious that some samples in which applicants carbon black is incorporated are similar to the hard channel black in properties, some are similar to the soft furnace black, while some'possess properties intermediate these two commercial types of black. A point of importance is that some of applicants samples are harder in respect to the physical properties of the rubber than the hard channel black sample. This point would indicate that tire tread stocks compounded with certain of applicants carbon blacks would'yield' better wearing and less easily abraded tires than the conventional high quality tires in which channel black is used. It will be noted, also, that applicants carbon black causes the compound to vulcanize more rapidly than the channel black, and for this reason, it appears that applicantfs samples Which were vulcanized for 60 and 90. minutes had reached a state of vulcanization more advanced than the regular control channel black samples. In one case, that of the B57 sample of carbon black of Table II, a 20 minute vulcanization was made which yielded a good rubber in all respects, even superior in most respects to the channel black sample vulcanized for thirty minutes for tire tread purposes. The zero set test as described in the literature and familiar to those skilled in'the art was the method used to'determine the extent of vulcanization. High resilience values are characteristically imparted to rubber by the soft furnace blacks. The higher resilience values among blacks of commerce I ordinarily go hand-in-hand withthe lower modulus values, forexample, the furnace blacks of Tables II and III, and vice versa, low resilience values ordinarily accompany high modulus values, as for example, the channel black of Table II. One of the outstanding properties of applicants blacks is their ability to impart to vulcanized rubber high modulus values and at the same time high resilience values. This property is extraordinary, as will be appreciated by those skilled in the art of rubber compounding.

Considering the data of Table'III, it may be seen that the samples vulcanized at 260 F., and having my carbon black incorporated therein possess very excellent properties for tire, tread stocks when compared to the channel black sample of Table II. This data also indicates that my black lends rapid vulcanizing properties to rubber compounds, and that these rubbers possess high modulusvalues along with highresilience.

Upon consideration of the data of Tables II and III, it is seen that certain of my carbon blacks are adaptable for making the type of rubber ordinarily requiring a soft black, the type of rubber-requiring hard blacks, and the type requiring intermediate blacks. These several types of carbon blacks were made in my apparatus and according to my process by certain and systematic variationsof theoperating conditions. One particular advantage of my process is that it is not limited to the making of one particular kind ortype of carbon b1ack,.as are present day commercial, processes, but in contrast is adaptable to the making of numerous types orkinds of carbon blacks, and these various kinds of carbon black may then be made to fit changing market, supply and demand conditions. Inaddition, anotherimportant advantage of my process is the very high yield of carbon black obtained which high yield isa definitestep forward-in the conservation of a natural resource.

An example in which pure methane was used as charge stock to my reaction chamber yielded 3 to 5 poundsof carbon black per 1000 cubic'feet of methane. The 3 pound yield calculated to 9.5% yield per 1000 cubic feet of reactant methane. The 5-pound yield amounts" to 15.8% of the available carbon. The 3'pound yield carbon was, however, somewhat superior in rubber making qualities-to the 5 pound carbon.

In contrast, thechannel processoperating on pure methane, as in the aboveexperiment, gave only 0.75 poundcarbon or about 2.4% yield per 1000 cubic feet of methane.

'In another example, residue natural gas from a gasoline extraction-plant, and a gas oil were used as charge'stock. The residue natural-gas was heated to approximately 2000 F. in, a preheater not shown in the drawings and a gas oil of about 18 A. P. I. gravity added dropwise or in a relatively small stream to this preheated gas during its passage from the preheater to the reaction chamber In. The gas oil was vaporized by the high temperature residue gas and this gasvapor mixture was charged into the reaction chamber as reactant gas alone or mixed with reactant air. Residue gas, as above, and air were entered into the chamber I0 through the tangential burners l5. By control of this operation, as heretofore disclosed, a very high yield of carbon black was obtained. From the total yield of black was subtracted the yield due to the residue gas, and the. remainder of the black calculated to 5 pounds black per gallon of gas oil. This combined black yielded rubber of excellent quality when made up and vulcanized as heretofore set forth.

Relating to the apparatus or more particularly to the reaction chamber H] as shown in the drawings, it is not intended to limit the chamber to the particular design as shown. The shape does not necessarily need to be cylindrical, but may be more oval in section or even rectangular to square. The tangential burners, in the case of small chambers, may be limited to one, or in larger chambers may be two or more, the number depending on the size of the chamber. When several burners are used, they can be distributed along the length of the chamber as shown in Figures 3 and 4, or they can be at the inlet end distributed around the circumference of the chamber. In this latter case, it may be desirable to give the fuel some velocity downstream with respect to the chamber by directing the burners at a slightly less angle than 90 to the longitudinal axis of the chamber The burner ports can be of any shape such as round, oval or rectangular. A rectangular burner has an advan tage over a round one in that a greater portion of the fuel stream enters tangentially with respect tothe inside surface of the chamber, this being true in the case of burners with cross sections having a large ratio of length to width and with the longer dimension of the cross section parallel to the longitudinal axis of the chamber. In one embodiment, a large number of tangential openings may be provided in the lining ofthe chamber and supplied with fuel from an annular space surrounding the lining. In another embodiment, a single rectangular burner extending throughout the length of the chamber can be used.

The products issuing from the chamber Hi can be cooled by any conventional means, such as mixing with a cool inert gas such as nitrogen, or with a spray of water. The position of the point of introduction of the cooling gases or water spray depends on the desired time of exposure of the carbon product to the hot gaseous products of combustion from the tangential flame. Ifpa separate quenching chamber is provided for each reaction chamber, it should preferably have about the same diameter as the chamber and have its axis in line with the axis of the reaction chamber. This arrangement permits the tangential flame to continue into the quenching chamber to keep the products in the central core from contacting solid surfaces until they are cooled.

Other gases than air can be used with the reactant fuel as well as with the tangential fuel, for example, oxygen enriched air or even oxygen alone.

As disclosed heretofore, my process is not limited to the use of natural gas as the carbon containing gas, while in addition to either dry gas, wet gas or raw gas as it comes from the well, or gasoline extraction plant or refinery residue gas, heavier hydrocarbons such as butane, or still heavier hydrocarbon products or fractions or even normally liquid hydrocarbons may be used, as for example, the gas oil previously disclosed. Oils heavier than the gas oil of commerce may be used as a source of carbon, as well as lighter oils, such as the kerosene fraction, heavy or light naphthas, or even the gasoline range of hydrocarbons. In addition, such materials as low temperature coal gas, coal tar distillates and 011' j shale gases and distillates may be used as charge stockto my process. 7

The air or gas, or both, in the fuel to, the tangential burners can be preheated as a means of introducing more, heat into the chamber. Fuel.

rich in air, or air alone, preferably preheated, can be used in any or all of the tangential burn-- ers. Enriching the said fuel with air was found to reduce the fuel rate required to keep the chamber walls free of carbon. When air alone is used in the tangential burners, the product has a grayish color in comparison to the very black channel product, but the yield of carbon black. is high. As desired, the fuel mixture to the tan-- gential burners may be allowed to burn Within. the chamber or in a separate combustion cham-- ber, the hot combustion gases then being conducted tangentially into said chamber. Since the functions of the tangential gases are to furnish heat to the chamber walls and to prevent deposition of carbon thereon, it is immaterial at what point the combustion takes place, as long as the gases reach the chamber walls in a properly heated condition.

One advantage of my process over the prior art lies in the fact that it makes possible the rapid conversion of hydrocarbons to carbon black out of contact with solid surfaces in extremely short reaction times and without depending on maintenance of streamline flow. I have verified that even under turbulent flow conditions a tangential layer of gas can be maintained to separate the wall and the gas occupying the central core of a cylindrical reaction chamber. The presence of a tangential gaseous layer may be readily demonstrated by producing a yellow flame in the central core and then introducing air through one or more tangential ports when a clear layer of air adjacent to the wall is visible. The thickness of this layer changes only little even if the amount of air introduced is two or three times the minimum required to establish the clear layer. This additional air over the minimum is apparently mixed with the reactant gas in the central core, and this fact is evidenced by the shortening of the yellow flame. If the air is introduced axially as a uniform layer next to the wall with a streamline flow in both the central flame and the air layer, a long diffusion flame results but a clear layer of air is maintained be tween the flame and the wall. However, as the velocities are increased into the turbulent flow range, the flame becomes shorter, the clear layer adjacent to the chamber walls disappears, and the flame is then in direct contact with the wall and carbon may be deposited thereon.

In my process, the operation at suflioiently high linear velocity of reactant gas as to give turbulent flow results in rapid transfer of heat into the moving body of reactant gas and decreases the time of reaction. This decreased time of reaction operates advantageously in my process since a much greater output of carbon black per chamber results, and a relatively large output of black per unit of chamber volume is characteristic of my reaction chamber and process of operation.

Operating under said turbulent flow conditions in the reactant gas stream has the advantage of making any given cross section of the stream normal to the direction of flow more nearly homogeneous with respect to states of decomposition, combustion, and dilution. In contrast, a diffusion flame, characteristic of other carbon black making processes, is likely to have much tar and unreacted gas in the center, a surrounding layer of substantially decomposed gas carrying good quality carbon, and an outer layer ofxcomnletely decomposedgas carryin overheated carbon. 7

When premixed fuel is used in the tangential burners, surface combustion on the chamber walls takes place thereby heating the walls to a very high temperature. These heated walls then heat .gthe reactant gases by radiation. An appreciable part of this surface combustion goes to CO2 and H20 and does not revert to CO and H2 because the carbon forming reactants do not mix completely' with the combustion products and because the time at elevated temperature is too short.

The tangential flame also has the function of diluting the products, particularly in the latter partof the chamber. This; dilution decreases the concentration, of any. undecomposed hydrocarhens and thus lessens the chance for carbon par- :ticle growth between the chamber and the, point inthe: cooling system, at which the products are cooled toa temperature below which'no further 16 Gi i- 2 i 120551 6- ;Mixing-ofthe reactant gas and the tangential .ilamewithin thechamber itself. has. been found .to, play-an important, role in my process. In addition to aiding in heat transfer, such mixing improves the-quality ofthe product, as for example, the amount of acetone extractable matter in the carbon black is readily controlled by regulating the extent of this mixing, the greater the extent of mixing the less the acetoneextractable.

Another advantage of this process over the prior, art is its. greater. flexibility as to controlling theoperation and as to control the quality of product. The properties of the product can be varied over a wide range by adjusting the fuel rate. to the tangential burner, the ratio of reactant. air-to-reactant gas,,gas and air preheat temperature, reaction chamber temperature, and cooling of the chamber product, etc. Using my apparatus'and the same raw materials, carbon blackvarying in properties fromthose of a. soft .thermaldecomposition black to thoseof ahard channel black was produced.

.While chambers varying in diameter from four andnnfirhalf inches to nineandone-half inches have. been successfully used, as disclosed. heretofore, .I .do not wish to limit my apparatus to these. sizes since other sizes both smaller and larger may be used. For chambers of large diameters and corresponding length, such as would be. used in commerce, the optimum number and arrangementvof tangential burners would need'to be determined Materialsl of construction, as for example, preheat furnace tubes, reaction chamber insulation and, lining, etc., may be selected from... among those, items commercially available and best suitedtothe operating, conditions as herein disclosed withoutdeparting from the scope of my invention. I

While the preferred apparatus and method, of operationfor carrying .out myinvention aredescribed inthis specification, it will be obvious to those, skilled in the art that there mayv be many possible variations of the apparatus and methodsof operation as may be learned from operating experience and yet remain within the intended spirit and scope of my invention, and limited only by the following claims.

I claim:

' 1. The process of. producing carbon blackcomprising introducing reactant hydrocarbon in the gaseous condition through an inlet tube at ap- '1 proximately the center of the :inlet end wall. of

a reaction chamber having an inlet endnwall;

carrying said inlettube; anoutlet. end, and a ing a gradualdiametric constrictionbetween the inlet-end Wall-and the outlet end,-and said inlet tubebeing' so positionedin said. inlet end wall as to form an annular space therebetween, the reactant hydrocarbon being introduced in a-direction substantially parallel to the longitudinal axis of the reaction chamber; introducingair into said annular space through a tube, thistube being so positioned as to direct the flow of air therethrough in a direction tangentto the outer wall of said annular space, and essentially in'a plane perpendicular to the longitudinal axis of said generally cylindrical chamber, said air preventing carbon deposition on said, inlet tube; introducing oxygen-containing gasintothe reaction chamber near the inlet end wall through a burner port and introducing further oxygen-containing gas into the reaction chamber through 1 another burner port, near the-diametric constriction. but on the downstream side thereof, said burner ports being so positioned as to direct the flow ofoxygen containing-gases therethrough in a directiontangent to the inner surface'of the side wall and with the predominating component of 'a motion in a plane perpendicular to the longitudinal axis of said generally cylindrical chamher, said oxygen-containing gas and a portion of the reactant hydrocarbon mixing to form a combustible mixture, and said further oxygencontaining gas and another portion of the reactant" hydrocarbon mixing to form a combustible mixture, burning these combustible mixtures to maintain the temperature of the reaction chamber-at'the carbon black forming temperature,

theoxygen-containing gases being introduced through said burner ports at a sufficiently high velocity and in sufficient quantities to maintain the flame and combustion products by centrifugal force adjacent the whole inner surface of the chamber sidewalls, thus forming a separating layer of said flame and combustion products between the side walls and the reactant gas mixture in the reaction chamber; cooling the eilluents of the reaction chamber to below the carbon black forming temperature and separating the carbon black from the products of combustion.

2. The process of producing carbon black comprising continously introducing a stream of gaseous hydrocarbon through the inlet end wall -ofa-reaction chamber having an inlet end wall,

containing. gas near the inlet end wall through a burner port, introducing further oxygen-containing gas into the reaction chamber through another burner port near the diametric constriction but on the downstream side thereof,

:said burner ports being so positioned as to directthe flow of oxygen-containing gases therethrough in a direction tangent to the inner surface of the side wall and with the predominat ing component of motion in a plane perpendicu1ar to, the longitudinal axis of'said generally cylindrical chamber, said oxygenecontaining gases and. a portion of the reactant hydrocarbon mixing to form combustible mixtures,-burning the combustion mixtures to maintain the temperature of the reaction chamber at the carbon black forming temperature, the oxygen-containing gases being introduced through said burner ports at sufficiently high velocities and in sufficient quantities to maintain the flames and combustion products by centrifugal force adjacent the inner surface of the chamber side wall, thus forming a separating layer of said flame and combustion products between the side wall and the reactant hydrocarbon in the reaction chamber, cooling the effluents of the reaction chamber to below the carbon black forming temperature and separating the carbon black from the products of combustion.

3. The process of producing carbon black comprising continuously introducing a stream of reactant hydrocarbon through an inlet tube at approximately the center of the inlet end wall of a reaction chamber having an inlet end wall, an outlet end, and a generally cylindrical side wall, the cross sectional area of the outlet end being substantially the same as the cross sectional area of the cylindrical reaction chamber at this point, said chamber having a diametric constriction of gradually decreasing diameter between the inlet end wall and the outlet end, the smaller diameter end of the constriction being in the direction of the outlet end; said inlet tube being so positioned in the inlet end wall as to form an annular space therebetween; the reactant hydrocarbon being introduced in a direction substantially parallel to the longitudinal axis of the reaction chamber; introducing oxygen-containing gas into said annular space through a burner tube, this burner tube being so positioned as to direct the flow of oxygen-containing gas therethrough in a direction tangent to the outer wall of said annular space and essentially in a plane perpendicular to the longitudinal axis of the reaction chamber, said oxygen-containing gas supporting combustion of at least a portion of the reactant hydrocarbon issuing from said inlet tube thereby preventing deposition of carbon thereon; introducing a mixture of gaseous fuel and at least sufiicient oxygen-containing gas for substantially complete combustion of said gaseous fuel into the reaction chamber near the inlet end wall through a burner port and introducing a further mixture of gaseous fuel and at least sufficient oxygencontaining gas for substantially complete combustion of said gaseous fuel into the reaction chamber through another burner port near the diametric constriction but on the downstream side thereof, said burner ports being so positioned as to direct the flow of gaseous fuel-oxygen containing gas mixtures therethrough in a direction tangent to the inner surface of the sidewall and with the predominating component of motion in a plane perpendicular to the longitudinal axis of said chamber, burning these combustible mixtures to maintain the temperature of the reaction chamber at the carbon black forming temperature, and said combustible mixtures being introduced through said burner ports at sufficiently high velocities and in suflicient quantities to maintain the names and combustion products by centrifugal force adjacent the inner surface of the chamber side wall, thus forming a separating layer of said flames and combustion products between the side walls and the reactant gas mixture in the reaction chamber; cooling the eflluents of the reactionchamber to below the 16 carbon black forming temperature and separating the carbon black from the products of combustion.

4. The process of claim 3 wherein said reactant hydrocarbon introduced through said inlet tube comprises a gas oil.

5. An apparatus for the production of carbon black comprising a generally cylindrical reaction chamber having the side wall thereof insulated, an insulated inlet end wall and an outlet end, said chamber containing an annular refractory member at a point between the inlet end and outlet end, said member having a conical bore having an inlet end the same size as said chamber and an outlet end having a substantially smaller inside diameter than that of the cylindrical re action chamber; the inlet end of the chamber carrying an inlet tube disposed at the approximate center thereof and axially of the chamber,

and the insulated side wall carrying a burner tube at the inlet end of the chamber and another burner tube at a point on the downstream side of said annular refractory member, the longitudinal axes of said burner tubes being essentially tangent to the inner surface of said side wall and approximately in a plane perpendicular to the longitudinal axis of the cylindrical chamber.

6. An apparatus as in claim 5 wherein the inlet tube is disposed in the inlet end wall.

'7. An apparatus as in claim 5 wherein the annular refractory member is at approximately a mid point of the inside length of the reaction chamber.

8. An apparatus as in claim 7 wherein the burner tube on the downstream side of the annular refractory member is substantially adjacent said annular member.

9. An apparatus for the production of carbon black comprising a generally cylindrical reaction chamber having the side wall thereof insulated, an insulated inlet end wall and an outlet end, said chamber containing an annular refractory member at a point between the inlet end and outlet end, said member having a conical bore having an inlet end the same size as said chamber and an outlet end having a substantially smaller inside diameter than that of the cylindrical reaction chamber, said inlet end wall carrying an inlet tube disposed axially and at the approximate center thereof and extending in a downstream direction from said wall, an annular ring of refractory adjacent the inlet end wall and extending in a downstream direction and concentric with the axes of the inlet tube and chamber and forming an annular space between said inlet tube and said refractory ring, a second inlet tube extending through the chamber side wall and through the refractory ring and so disposed in the latter that the longitudinal axis of said tube is tangentto the inner Wall of said refractory ring and approximately perpendicular to the longitudinal axis of the reaction chamber; the insulated side wall carrying a burner tube at the inlet end of the chamber and another burner tube at a point on the downstream side of said annular refractory member, the longitudinal axes of said burner tubes being essentially tangent to the inner-surface of said side wall and approximately in a plane perpendicular to the longitudinal axis of the cylindrical chamber.

10. An apparatus as in claim 9 wherein the annular refractory member is at approximately a mid point of the inside length of the reaction chamber.- I

cent said annular member.

12. The process of producing carbon black comprising continuously introducing reactant" hydrocarbon in the gaseous state into the inlet;- portion of a reaction chamber having an inlet portion, a generally circular transverse crosssec-i tion, an outlet end, and an interior passage unobstructed from'and including said inlet portion to and including said outlet end except foif an intermediate conical restrictor, continuously flowing the reactant hydrocarbon the major por tion of the length of said chamber inside said chamber from said inlet portion to said outlet end in a direction substantially parallel to the longitudinal axis of the reaction chamber; intro-, ducing oxygen-containing gas into the reaction chamber near the inlet portion through a burner port, said burner port being so positioned to. direct the flow ofsaid oxygen-containing gasiin a direction tangent to the inner surface of the side wall and with the predominating component of motion in a plane perpedicular to the longi-' tudinal axis of said cylindrical chamber, bum' ing the resulting mixture of reactant hydrocarbon and oxygen-containing gas to maintain the temperature of the reaction chamber at a carbon black forming temperature, gradually constricting said resulting mixture to a, smaller diameter, introducing more oxygen-containing gas into the reaction chamber near and after the point of constriction through a burner port in a direction predominately tangent to the wall of said reaction chamber, the oxygen-containing gas being introduced through said burner ports at a sufli-ciently high velocity and in suflicient quantity as to maintain by centrifugal force the flame and combustion products produced by the oxygen-containing gas adjacent substantially the whole inner surface of the chamber from said inlet portion to said outlet end thus forming a separating layer of said flame and combustion products between the side wall and the reactant mixture in the reaction chamber, cooling the efliuents of the reaction chamber to below the carbon black forming temperature and separating the carbon black from the products of combustion.

13. The process of claim 12 wherein said reactant hydrocarbon introduced into the inlet portion of said reaction chamber comprises a gas oil.

JOSEPH C. KREJCI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,368,827 Hanson Feb. 6, 1945 2,368,828 Hanson Feb. 6, 1945 2,375,795 Krejci May 15, 1945 

1. THE PROCESS OF PRODUCING CARBON BLACK COMPRISING INTRODUCING REACTANT HYDROCARBON IN THE GASEOUS CONDITION THROUGH AN INLET TUBE AT APPROXIMATELY THE CENTER OF THE INLET END WALL OF A RACTION CHAMBER HAING AN INLET END WALL OF CARRYING SAID INLET TUBE, AN OUTLET END, AND A GENERALLY CYLINDRICAL SIDE WALL, SAID CHAMBER HAVING A GRADAL DIAMETRAIC CONSTRUCTION BETWEEN THE INLET END WALL AND THE OUTLET END, AND SAID INLET TUBE BEING SO POSITONED IN SAID INLET END WALL AS TO FORM AN ANNULAR SPACE THEREBETWEEN, THE REACTANT HYDROCARBON BEING INTRODUCED IN A DIRECTION SUBSTANIALLY PARALLEL TO THE LONGITUDINAL AXIX OF THE REATION CHAMBER; INTRODUCING AIR INTO SAID ANNULAR SPACE THROUGH A TUBE, THIS TUBE BEING SO POSITIONED AS TO DIRECT THE FLOW OF AIR THERETHROUGH IN A DIRECTION TANGENT TO THE OUTER WALL OF SAID ANNULAR SPACE, AND ESSENTIALLY IN A PLANE PERPENDICULAR TO THE LONGITUDINAL AXIS OF SAID GENERALLY CYLINDRICAL CHAMBER, SAID AIR PERVENTING CARBON DEPOSITION ON SAID INLET TUBE, INTRODUCING OXYGEN-CONTAINING GAS INTO THE REACTION CHAMBER NEAR THE INLET END WALL THROUGH A BURNER PORT AND INTRODUCING FURTHER OXYGEN-CONTAINING GAS TO THE REACTION CHAMBER THROUGH ANOTHER BURNER PORT NEAR THE DIAMETRIC CONSTRITION BUT ON THE DOWNSTREAM SIDETHEREOF, SAID BURNER PORTS BEING SO POSITIONED AS TO DIRECT THE FLOW OF OXYGEN-CONTAINING GASES THERETHROUGH IN A DIRECTION TANGENT TO THE INNER SURFACE OF THE SIDE WALL AND WITH THE PREDOMINATING COMPONENT OF A MOTION IN A PLANE PERPENDICULAR TO THE LONGITUDINAL AXIS OF SAID GENERALLY CYLINDRICAL CHAMBER SAID OXYGEN-CONTAINING GAS AND A PORTION OF THE REACTANT HYDROCARBON MIXING TO FORM A COMBUSTIBLE MIXTURE, AND SAID FURTHER OXYGENCONTAINING GAS AND ANOTHER PORTION OF THE REACTANT HYDROCARBON MIXING TO FORM A COMBUSTIBLE MIXTURE, BURNING THESE COMBUSTIBLE MIXTURES TO MAINTAIN THE TEMPERATURE OF THE REACTION CHAMBER AT THE CARBON BLACK FORMING TEMPEATURE, THE OXYGEN-CONTAINING GASES BEING INTRODCED THROUGH SAID BURNER PORTS AT A SUFICIENTLY HIGH VELOCITY AND IN SUFFICIENT QUANTITIES TO MAINTAIN THE FLAME AND COMBUSTION PRODUCTS BY CENTRIFUGAL FORCE ADJACENT THE WHOLE INNER SURFACE OF THE CHAMBER SIDE WALLS, THUS FORMING A SEPRATING LAYER OF SAID FLAME AND COMBUSTION PRDUCTS BETWEEN THE SIDE WALLS AND THE REACTANT GAS MIXTURE IN THE REACTION CHAMBER; COOLING THE EFFLUENTS OF THE REACTION CHAMBER TO BELOW THE CARBON BLACK FORMING TEMPERATURE AND SEPARTING THE CARBON BLACK FROM THE PRODUCTS OF COMBUSTION. 